Our goal is to investigate the miRNA profiles of prostate tumors and the normal epithelium to evaluate if there are differences in specific miRNA expression patterns of tumors with different grades of differentiation and different biological beavior. Prostate cancers will be manually microdissected to obtain pure populations of tumor cells as well as available normal epithelium distant to the tumor area. Histological features such as Gleason score, presence of perineural, lymphatic invasion, extracapsular or seminal vesicle invasion were also evaluated and recorded for each case. Differentially expressed miRNAs will be defined as those with a two-fold change (up or down) and a p value &lt;0.05. Different miRNAs expression profiles will include comparison between the low grade tumors (Gleason score 6 and 7) vs. high grade (Gleason score 8 and 9) lesions. Then, each tumor group will be compared with their respective group of normal epithelium.